Digital nonlinearity compensation in the presence of polarization mode dispersion

The impact of polarization mode dispersion (PMD) on the performance of coherent transmission systems employing different digital nonlinearity compensation (NLC) schemes is numerically investigated for a seven-channel PM-16QAM Nyquist-wavelength division multiplexing system at 256 Gbit / s. In these nonlinearity compensation schemes, the digital signal processing is divided between the transmitter (Tx) and receiver (Rx) with different splitting ratios. We demonstrate that by splitting the NLC equally between the Tx and Rx, one can always obtain the best performance improvement regardless of whether PMD is present or not. Results of 1000-km dispersion-unmanaged transmission show that when fiber PMD is equal to 0.05 ps / km, splitting the NLC can give a signal-to-noise ratio improvement of 1.1-dB over receiver-side NLC, while it is 0.9 dB for 0.1 ps / km of the fiber PMD coefficient.